A copartnership



0.1. HEISER.

FILAMENT TYPE 0F HEATING ELEMENT.

APPLlCAT-LON FILED JUNE 20, 191B.

Patented Nov. 25, 1919.

2 SHEETS-SHEET l.

rr Ley-S C. I. HEISER.

FILANIENT TYPE 0F HEATING ELEMENT.

APPLICATION FILED JUNE 20. ISIS.

Patented Nov. 25, 1919.

2 SHEETS-HEET 2.

UNITED sTATEs PATENT oEEicE CHARLES J. HEISER, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO PACIFIC MANUFAC- TURIN G & ELECTRIC COMPANY, OF LOS ANGELES, CALIFORNIA, A COPARTNERSHIP.

FILAMEN T TYPE OF HEATING ELEMENT.

To all whom t may concern,

Be it known that I, CHARLES J; HEIsER, a citizen of the United States, residing at Los Angeles, in the county of Los Angeles and State of California, have invented a new and useful Filament Type of Heating Element, of which the following is a specification. i

My invention relates to the art of heating by the use of electric current, and more particularly to the art of heating liquids. The principal object of my invention is to provide a novelA form of immersion heating element vand method of making same for use in this art.

' In the art of heating liquids by electric current, it is necessary to use conductors which are heated to a high temperature, and it is further necessary to electrically insulate these conductors from the liquid in which they are immersed. It is further necessary that the electrical insulation shall be formed of a material, and that this material shall be so used that the conduction of heat from the heated conductor to the surfaces at which the heat is to-be utilized shall be as great as possible. It is a further object of my in-V vention to provide an electric heating element which shall have a very high electrical insulation value combined with a very high heat conductivity.

It is further necessary in such a heating element that it be so constructed that the ex` p ansion of the various parts as they are heated, and the contracting of these parts )as they are cooled, will not injure either the insulation or the conductor, and it is a further object of my invention to provide aheating element which can be alternately Vheated and cooled a large number of times without danger of injuring any portion of the element.

It is a further object of my invention to provide a heating element in which a round wire is used. as I have found that such wires are much superior to flat strips in that the round wire has no sharp edges to cut through the insulating material.

I have further found that sheet mica forms an ideal insulating material for use in heating devices, in that it has a very high dielectric value, and that consequently very Specification of Letters Patent.

necessary thermal conductivity. Mica ishowever, brittle, and while it can safely be `bent into cylindrical form, it cannot be sharply bent without danger of breaking.

It is a further object of my invention to so construct the heater that the sheet mica is bent in a single plane, and so that the bends in the mica shall be as gradual as possible to prevent breaking down the insulation at the bends. 'f

It is further desirable in a heating element to maintain the temperature of all parts of the wire carryingthe current at the 'same temperature, as by so doing the average temperature of the wire is also the maximum temperature. By Amaintaining the entire wire at such a maximum temperature, which is fixed by the physical characteristics of the materials used, a maximum capacity is obtained in a minimum of space and with a minimum of material. To maintain the entire wire at this maximum temperature, it is necessary that the heat conduction conditions be identical throughout the wire and this condition is very closely approximated in my invention.

My invention comprises a heating element which is covered by a metal sheath, this metal sheath being electrically insulated from the conductor, so that it may be immersed in various liquids, and may particularly be immersed in an electrolyte without danger of the electrolyte coming in contact with the conducting wire.

It is a further object of my invention to provide means by which this sheath is utilized to retain the insulating material and the conductors in their proper relationship. and in which the sheath is so formed and placed as to have an unusually perfect thermal contact with the insulating material.

Further objects and advantages will be .nade evident hereinafter.

Referring to the drawings which are for illustrative purposes only,

Figure l is a side elevation of a heating element embodying my invention.

Patented Nov. 25, 1919. Application filed .Tune 20, 1918. Serial No. 241,067.

Fig. 2 is a similar view partially in section.

Figs. 3 to 8 inclusive are enlarged sections taken on a plane represented by the line 3-3 of Fig. 1, and showing successive steps in the manufacture of my invention.

Fig. 9 is a -perspective view showing the various parts as they appear at one stage of their manufacture.

Fig. 10 is a view on a still more enlarged scale showing the method of constructing the heating element at the point of emergence of the conductors.

Fig. 11 is a View on a similar scale as Fig. 9 of a section through the heater, this section being taken on the line 10-10 of F ig. 1.

Fig. 12 is a diagrammatic view showing the method of securing the heating element in a boiler or the like.

Fig. 13 is a section on the line 13-13 of Fi 12. P

he heating element consists of four parts, namely, the conductor 11, the leads 12, the insulating material 13, the retaining member 14 and the sheath 15.

The conductor 11 is bent into a U shape, as shown in Fig. 1, the bend 16 being fairly short, and the limbs 17 and 18 of the U being relatively long. The leads 12 are slipped over the wire 11 at the point of emergence 19' of these wires from the heating element.

The heating element will perhaps be better understood after the following description of the method of manufacture:

The retaining member 14,y which is 0f thin sheet copper and which is somewhat' shorter in length than the sheath 15 is bent to form -a metal trough, as shown in Fig. 3. The insulating material 13, which consists of thin sheets of mica is then placed inside the metal trough as shown in Fig. 4, thus forming an insulating trough. In practice I use three layers of sheet mica, which are laid as shown in Fig. 4, and in which the joints are broken as shown at 21, 22 and 23 in Fig. 8. By using sheet mica of uniform thickness and of uniform length and width, Y

I am able to form an insulating trough, in

. which the wire 11 can be placed, the limbs 17 and 18 of the wire, lying as shown in Fig. 5. B v the use of a suitable tool. I then.

bend one side of the insulating trough, indicated at 24 in Fig. 5, over into the position shown in Fig. 6.. In so bending the mica and the retaining member 14, I am careful to start the mica with a gradualbend as shown at 25 in Fig. 6, thus preventing it from breaking at the point of bending indicated by the dotted line in Fig. 6. It will be noted that in Fig. 6, the ends of the mica sheets shown at 27 lie against the limb 18, and are of approximately the same total thickness as the diameter of the wire, thus tending to hold it in position and prevent it from becoming displaced. With the material in the position shown in Fi 6, I then bend the other side of the insu ating material with its retaining member, as shown at 29 in Fig. 6, over until they assume the position shown in Fig. 7. It will be seen that the parts then have an oval section with straight sides, and it will be further seen that the limbs 17 and 18, are completely wrapped in sheet mica, and that the creepage distance to the retaining member 14 over the surface of the mica at any. point, is very long. With the heatin element partially completed, as shown in Fig. 7, it is possible to slip the metal sheath 15 over the retaining member 14 until the parts assume the approximate position shown in Fig. 2, with the insulating material 13 projecting slightly beyond the sheath 15 and the retamin member 14, as shownat 28 in Fig. 2. l

then apply considerable pressure in the diy crimping the sheath 15 in between the limbs 17 and 18, and further compacting the mica and forcing out the air from the interior of the sheath 15 and giving a better thermal contact. I have further found by bending in the sides of the sheath 15, as' shown in Fig. 8, that there is little likelihood of their springing a art. This is due to the inherent tendency o a curved elastic metal member to elongate in the direction of its convexity.

It will be seen that by constructing the element in this manner and by applying considerable pressure in the direction of the arrows 30 and 31, I am able to produce a very compact heating element, and one having a high thermal conductivity due to the close and intimate. contact of the insulating material 13 with the conductor 11, and the very perfect thermal contact between the sheath 15, the retaining, member 14 and the insulating material 13. J In practice I use a flattened tube for the sheath 15, and after the insulating material and wire have been put in place inside ythe sheath, I flatten it down, as shown in Fig. 10, leaving a small V shaped groove, as shown at 32, in which I place silver solder 33. thus very effectually and completely sealing the lower end of the tube so that fluids cannot enter it.

After the heating element is completed, it may be used as shown in Fig. 12, in which the sheath 15 is shown soldered into a. threaded plug 35 and making a water tight connection therewith. This plug 35 is cylindrical, as shown in Fig. 12, and may be threaded into a fiange 36 which is secured on a water tank or a receptacle containing any liquid. When so utilized a very high current density may b'e used in the conductor 11, as the heat transference from the conductor 11 to the sheath 15 is very eicient. Due to this high effeency of heat i transfer and this high current density, I am I tween said conductors and thereby separatable to use a minimum of material to produce a maximum result.

I claim as my invention:

l. A heating element comprising a Wire bent in U shape, insulating material surrounding said Wire and separating the straight limbs of said U shape, a metal retaining member wrapped partially around said insulating material, and a metal sheath surrounding said retaining member.

2. A heating element comprising a wire bent in U shape, insulating material sur'- rounding said Wire and separating the straight limbs of said `U shape, a metal retaining member Wr-apped partially laround said insulating material, and a metal sheath surrounding' said retaining member, said metal sheath being crimped in on either side thereof in such a mannery as to compress said insulating material and improve the thermal conductivity of the element. Y

3. Insulation for a heating element lhav` ing tw o parallel conductors, said insulation comprising a sheety of insulation; the inner edge of said Sheet occupying the Space be# ing them, the sheet also surrounding each of said conductors and vhaving its outer end lapped over said inner end.

et. A heating element comprising a Wire bent in vU form thusforming two parallel conductors, insulation as specified in claim 3, and a metal retaining member wrafpped around said insulation in such a manner as to holdit 4in place.

5. A heating element comprising a Wire bent in U form thus `forming two parallel conductors, insulation as 'specified in clailn 3, and a metal sheath surrounding 'said insulation.

6. A heating element comprising a Wire bent in U form thus forming two parallel conductors, insulationf as specified in claim 3, a metal retaining member clenched around saidI insulation, and metal sheath clenched around said retaining member.

In testimony whereof, I have hereunto set my hand at Los Angeles, California, this 13th day of June, 191'8.

CHARLESJIHEISER. 

